This invention relates to the treatment of minerals and is concerned with a process for the separation of one or more components of a mixture of mineral components from the other components and, more particularly but not exclusively, is concerned with a process for separating from crude kaolinitic clay minerals components present therein as impurities.
It is well known to separate impurities from crude minerals by froth flotation processes. Generally in a froth flotation process an aqueous slurry of the crude mineral is treated with a reagent (known as a collector) which is selectively adsorbed onto the impurities (which it is desired to separate from the desired mineral) and which gives the impurities a hydrophobic surface; examples of commonly used collectors are oleic acid, long chain amines and suphonated petroleum hydrocarbons. The reagentised crude mineral slurry thus produced is the agitated in the presence of air and a froth is formed, and the impurities, which now have a hydrophobic surface, enter the air/water interface existing between bubbles of air and the aqueous medium. When a bubble of air rises to the surface of the reagentised crude mineral slurry the impurity goes with it. The froth appearing at the surface of the reagentised crude mineral slurry can then be removed and separation of the impurities from the mineral may thus be achieved. However, with fine minerals, i.e. minerals composed predominantly of particles smaller than about 50 microns, such as the clay minerals, separation of impurities by a froth flotation process is not very efficient and is difficult to achieve. Consequently, there have been devised other types of process for separating impurities from fine minerals: and one type include the steps of (a) adding to an aqueous slurry of the crude mineral a hydrophobic collector for the impurities in the crude mineral and (b) mixing the slurry of crude mineral containing the collector with an organic liquid which is immiscible with water whereby the impurities, which have adsorbed thereon the hydrophobic collector, are selectively extracted by the organic liquid leaving the purified mineral in the aqueous phase. Two processes of this type are described in U.S. Pat. No. 3,432,030 and in British Patent Specification No. 1,222,508. We have found, however, that such processes may be very sensitive to changes in the conditions employed and unless these are closely controlled satisfactory separations and yields are not readily obtained.